We like to replace the spark plugs and oil prior to any baseline test to ensure consistency and optimum performance. But there are a couple of hurdles. First, this car takes 24 plugs and it’s a six-hour job to do it. At the dealer, this could cost you north of $1,200. Thankfully, Sparkplugs.com sells factory identical NGK R IFR6Q-G Iridium plugs for half the dealer price, and an independent service center like the one we found, European Motorsports, will save you even a few hundred more in labor.

Our second hurdle was the intercooler pump. Unfortunately, boosted V12 and V8 Mercs are plagued with failing intercooler pumps that seem to let go at random, and mine was no exception. As soon as we took delivery we plugged in our Actron Pro Elite OBD-II scanner. The intake air temps soaring to over 100 degrees F above ambient—and the MAF seeing less and less air density after each pull—told the story. This was not good for performance, let alone for our testing.

It’s good for us then that Renntech sells a full intercooler upgrade, featuring a pump that provides more than twice the flow and much greater durability than the factory pump. Additionally, the kit features a second heat exchanger for double the stock capacity, and includes all adaptive hardware.

The kit runs about $4,000 from Renntech, and European Motorsports’ technicians were up to the task of installing it. Thanks to the intercooler upgrade, our intake air temps consistently hover between 20-30 degrees over ambient. This is probably the most important upgrade for any V12 Biturbo or V8 Kompressor Mercedes.

Vehicle Data

Engine: 5.5-liter V12 twin-turbocharged

Photo 3/10 |
The CL blackened grille from 55 Tech Motors is a simple aesthetic upgrade that, coupled with Renntech Monolite wheels and wider General Tire AS-03 rubber, makes a huge improvement to the looks of the front end.

With good IATs, new plugs and fresh oil, we were set for baseline testing at Modified by KC in Kansas City. On MKC’s 424x dyno we set the car into its factory “dyno mode” via the steering wheel buttons (how cool is that). This deactivated all the electronic gremlins that would otherwise freak the car out.

After the session, we were shocked to see over 470 whp through the auto tranny. This may answer the question behind our 54 lb/hr MAF readings, which would indicate roughly 540 hp. Renntech even tells us that the ’03 Mayach 57, rated at 550 hp, doesn’t make more boost than an S600, and is the same. Still, 470 whp through the auto tranny for a 493-hp car is definite sandbagging by Mercedes.

While Fourth gear pulls with this car, which yield 15-20 whp less, would have been preferred because of how quick Third gear is, the factory 130-mph governor makes it impossible to note any top end gains. Third gear alone maxes out at a whopping 115 mph, so at 130 mph a Fourth gear pull ends too prematurely while the car remains stock.

As soon as baseline testing was over we eagerly overnighted the engine ECU and tranny ECU (aka TCU) to Renntech, which had it back in our hands in less than 48 hours for testing. The firm flashes the engine ECU with new boost and fuel/ignition calibrations, and their TCU upgrade unlocks the max torque allowed through the transmission, much like AMG does for the newer biturbo 6.0-liter motors. After all, we’re told the newer cars still use the same bulletproof unit. The TCU upgrade also features a full manual mode, which is unavailable in stock form and makes dyno testing a little challenging.

On my way back to the dyno I gave the throttle a couple of blips and could instantly feel the difference, and the Actron scanner was now registering 64 lb/hr through the MAF sensor. The newfound power is at a near-scary level, and one could start to worry about engine longevity. But a quick glance at the ignition values at wide-open throttle and you’ll see around -12 degrees of timing (yes, negative 12). These engines are not even trying.

While the majority of the gains happen down low, you still enjoy an average increase of 50 whp from midrange on up.

To complete Renntech’s Stage 3 package we installed its beautiful carbon-fiber intake kit, featuring two new carbon boxes with a high-flow filter element in each. Complemented with a full carbon cover for the intercoolers as well as the front of the engine, the carbon bling under the hood is instantly noticed by everyone when the hood is popped open.

During testing we noticed the car wanted to hit the higher numbers but little fluctuations weren’t helping the intake’s gains. While the delta from 3800 rpm on averaged just under 5 whp, we’d bet that with more of a ram-air effect from the road at high speed this intake should definitely show more consistent gains in the mid-teens.

Conclusion

With simple bolt-ons, this car is significantly faster. Down low it’s a torque monster but the gains from 4000 rpm onward is what tells the true story of straight-line acceleration. In this car’s case, it still averaged over 50 whp—and we think maybe even a little bit more with the intake at high road speeds. Off the dyno and in the real world this equated to a 0.8-second improvement in the 60-120 mph acceleration test, now at 8.5 seconds—that’s knocking on the door of a 2010 Porsche 997.1 Turbo.

In acceleration testing using our VBOX PerformanceBox, our baseline testing, using our all-season tires, completed 0-60 mph in 4.4 seconds and the quarter-mile in 12.7 at 114.1 mph. With the ECU, TCU and intake upgrade, these numbers improved to 4.1 seconds and 12.2 at 118.6 mph. With this kind of acceleration, our Renntech S600 is the ultimate family Q-ship. Next time, we’ve got one last upgrade up our sleeves that will improve acceleration even further.